A lot of them were. A mix of Scots-Irish, English, Scots, and Irish. Most were privates in the militia, one appears to be Continental Line, and one an officer in the Line and later the Virginia militia.
Have you read Webb's book Born Fighting? A great book for those of Scots-Irish heritage (the "invisible" ethnicity, being the American type). David Hackett Fischer's Albion's Seed is also a valuable book, Webb drew heavily from it.